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1zrq

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[[Image:1zrq.gif|left|200px]]
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{{STRUCTURE_1zrq| PDB=1zrq | SCENE= }}
{{STRUCTURE_1zrq| PDB=1zrq | SCENE= }}
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'''Escherichia coli Methylenetetrahydrofolate Reductase (reduced) complexed with NADH, pH 6.0'''
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===Escherichia coli Methylenetetrahydrofolate Reductase (reduced) complexed with NADH, pH 6.0===
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==Overview==
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Methylenetetrahydrofolate reductases (MTHFRs; EC 1.7.99.5) catalyze the NAD(P)H-dependent reduction of 5,10-methylenetetrahydrofolate (CH(2)-H(4)folate) to 5-methyltetrahydrofolate (CH(3)-H(4)folate) using flavin adenine dinucleotide (FAD) as a cofactor. The initial X-ray structure of Escherichia coli MTHFR revealed that this 33-kDa polypeptide is a (betaalpha)(8) barrel that aggregates to form an unusual tetramer with only 2-fold symmetry. Structures of reduced enzyme complexed with NADH and of oxidized Glu28Gln enzyme complexed with CH(3)-H(4)folate have now been determined at resolutions of 1.95 and 1.85 A, respectively. The NADH complex reveals a rare mode of dinucleotide binding; NADH adopts a hairpin conformation and is sandwiched between a conserved phenylalanine, Phe223, and the isoalloxazine ring of FAD. The nicotinamide of the bound pyridine nucleotide is stacked against the si face of the flavin ring with C4 adjoining the N5 of FAD, implying that this structure models a complex that is competent for hydride transfer. In the complex with CH(3)-H(4)folate, the pterin ring is also stacked against FAD in an orientation that is favorable for hydride transfer. Thus, the binding sites for the two substrates overlap, as expected for many enzymes that catalyze ping-pong reactions, and several invariant residues interact with both folate and pyridine nucleotide substrates. Comparisons of liganded and substrate-free structures reveal multiple conformations for the loops beta2-alpha2 (L2), beta3-alpha3 (L3), and beta4-alpha4 (L4) and suggest that motions of these loops facilitate the ping-pong reaction. In particular, the L4 loop adopts a "closed" conformation that allows Asp120 to hydrogen bond to the pterin ring in the folate complex but must move to an "open" conformation to allow NADH to bind.
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{{ABSTRACT_PUBMED_16114881}}
==About this Structure==
==About this Structure==
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[[Category: Reductase]]
[[Category: Reductase]]
[[Category: Tim barrel]]
[[Category: Tim barrel]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 17:59:23 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Jul 27 13:16:06 2008''

Revision as of 10:16, 27 July 2008

Image:1zrq.png

Template:STRUCTURE 1zrq

Escherichia coli Methylenetetrahydrofolate Reductase (reduced) complexed with NADH, pH 6.0

Template:ABSTRACT PUBMED 16114881

About this Structure

1ZRQ is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.

Reference

Structures of NADH and CH3-H4folate complexes of Escherichia coli methylenetetrahydrofolate reductase reveal a spartan strategy for a ping-pong reaction., Pejchal R, Sargeant R, Ludwig ML, Biochemistry. 2005 Aug 30;44(34):11447-57. PMID:16114881

Page seeded by OCA on Sun Jul 27 13:16:06 2008

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